eucaryote
New member
More times than not, I see people asking questions on this forum in regards to getting more oxygen into their water. Oxygen itself is a cellular poison, there is no disputing this, it's in nearly every chemistry text book. All eukaryotic organism have developed a variety of mechanism to protect themselves. Often times as gardeners we tend to over do things, wanting what is absolutely best for our plants, but end up doing more harm than good. At what point though do we have too much oxygen?
From a chemical stand point, gas solubility in water is proportionate to pressure and temperature; introducing water at the bottom of a 30-ft standpipe for example will double the pressure, but since the bubbles will quickly rise to the surface, the full extent of the increased solubility will not be realized unless the higher pressure is maintained at a constant rate. The rate as opposed to the extent of the transfer of said gas into liquid is proportionate to the contact time and interfacial surface area. Surface agitation is not the end all determining factor here. The latter is inversely proportational to the cube of the bubble radius, so delivery of the gas in a form of tiny bubbles is far more rapid than for an equivalent volume of larger bubbles or solid stream.
To break that down for some of you that may be on your second bowl by now, airstone versus open line reaches the same goal eventually, but the airstone is the fastest most efficient method due to the spread of bubbles. I'm sure this has been covered in this forum, but I want to make it definitively clear.
At the ideal temperature of 20-22 celcius (68-71.6 fahrenheit) the water can only hold about 9 ppm dissolved oxygen. We can temporarily raise the dissolved oxygen levels by chemical reaction, such as adding H2O2 or more permanently raise it by causing waves at the surface with air pressure... Biochemical oxygen demand for the cannabis plant is only about 7 ppm to flourish in a constant water suspension. Watching frothing bubbles in a bucket is sure neat, and might sound relaxing for the first hour or so, but all you really need is enough air to have a light champagne sparkle that hits the lid of your container just barely. When you lift your lid after a day, and water drips at all, you're good. Before the nay-sayers in the crowd dismiss me as a lunatic, start shouting that I am a heretic and their crazy powerful pumps and powerheads own all; I'll tell you a little about what I did so you can reproduce it yourself.
My first grow involved four 18 gallon Rubbermaid containers and four Tetra Tec DW96-2 air pumps and 16 el-cheapo Wal-Mart airstones. I noticed something when one of my pumps failed (one of the diaphragms tore,) and I was forced to canabilize a cheap pump from my fish tank (sorry cichlids, my ladies need it more than you,) I had far less surface agitation/water movement, but my plants did absolutely fine all through the rest of their vegetative growth and flower stages. Curiousity got the best of me after this event... I went all mad scientist on the ladies with a gang valve to control the flow rate into the tub. Bare with me here, I am trying to explain it as simple as I can, but I sometimes have problems talking to the people outside of the walls of my head. hoo-hoo!
The Azide-Winkler method is widely known to the majority of chemists, and here's a break-down for you non-chemically inclined people... You start out with a 300 mL nalgene (or glass) bottle that has an air tight seal or stopper, ensuring that it has time to settle and no bubbles are visible. You generally don't want any bubbles when collecting your water sample, but sometimes it's unavoidable. I turned off my air pumps about 20 minutes before I collected my test samples. When the bubbles have settled, add 2 mL of manganese sulfate to your bottle by inserting a standard calibrated chemical dropper just below the water surface. Be careful though, if your re-agent is added above the surface you will introduce oxygen and your sample will become invalid. Squeeze the dropper slowly ensuring there are no bubbles being formed. Add 2 mL of alkali-iodide-azide re-agent in the same manner, remember, no bubbles! Close your bottle up gently, and mix it via inversion (turn it upside down, then turn it upside down again.) If you see any air bubbles, game over, start again. You'll start to see a cloud of brownish-orange junk. When it settles to the bottom, mix it via inversion again. Let it settle for a short period. I usually play tetris on my phone until I lose, then get back to it. Add 2 mL sulfuric acid via a chemical dropper from ABOVE the surface of the water. Close your bottle again, invert it over and over again to mix. At this point the sample can be stored for 7-12 hours in a cool dark place [this is dependent on your seal]. If you're anything like me, it's time to go crack a beer and eat a burger because you had to start over so many $%@* times. In a glass container, titrate 200 mL of the sample with sodium thiosulfate until it's a pale straw color. Titrate it slowly with your titrant solution one drop at a time into the container, stiring very gently just to make a swirl after each drop. Add 2 mL of starch solution, a blue color should be coalescing. Slowly titrate the solution until your sample turns clear. Only one drop too many of titrant will destroy your blue color, so be careful that each drop is fully mixed into your solution before adding the next. I generally do this in front of a white wall, or over a piece of high intensity white inkjet paper just to be absolutely sure of the colors in the container (I do the same thing with those annoying color pH test kits). The total concentration of dissolved oxygen is equivalent to the number of mL of titrant used. Each mL of sodium thiosulfate added equals about 1 ppm dissolved oxygen.
Utilizing the above methodology for measurement, I've established that nearly every strain of cannabis I have grown in the past 6 years only requires 7 ppm total dissolved oxygen. I gave up on looking for differences in 7 vs 14 ppm dissolved oxygen in DWC containers after seeing six different strains of four plant test samples per strain perform essentially the same. One thing that more dissolved oxygen does help with though, is keeping silly organisms like pythium in check. I'm sure you're already saying "duh!" or something like that in your head, but for the record I always introduce H2O2 every water change so I rarely worry about it in the long run. Die little eukaryotes, die! It also manages to keep my roots nice and white like my teeth. I urge people to re-create my experiment and test some rooted clones to see if you have any strains/phenotype that require or respond to more oxygen. The following strains were tested for 7 ppm survivability with no slow down in observable growth rate (subjective I know, but I went by height, internode spacing, stem thickness, and total plant diameter):
Skunk [red hair], reminded me of the 80s indoor strain that were so common, bag seed from a friend
Nirvana White Rhino
Nirvana AK-48
Nirvana Pure Power Plant
Reservoir Sour Diesel
Sensi Silver Haze
If we can form some type of database of oxygen level requirements for our plants, growing efficiency and sanity (because air pumps are loud) will increase. None of my plants showed any sign of slow down until levels reached 6 ppm, at which point growth rates during vegetative stage were days behind the other clones, but still surviving. At 4 ppm, plants began to droop as if they were overwatered and drowning. It wasn't until 2 ppm that I could reliably commit the horrible act of killing my ladies.
I think this is attributed to the roots getting added oxygen from hanging freely in the space between the water and the net pots, increasing their survivability chances. Too bad that they were basically eating themselves, but didn't live long enough to show me what they were eating. More oxygen than 14 ppm, did something for those that are wondering. It increased evaporation rate! (duh, a more gaseous state = higher evaporation) I couldn't raise the levels high enough to actually do harm to the plants, but I did notice at 14 ppm constant that my nutrient ppm seemed to not drop as fast. Possibly the plants not being able to eat fast enough due to a defensive mechanism? Maybe the evaporation rate causing the nutrient solution to be more volume versus water available? Got me, the girls wouldn't tell me if they were not getting what they needed or not, they stayed green. Any plant physiologists in the crowd want to chime in? I keep telling my plants that communication is the key to every healthy relationship, but I always get the cold shoulder. 
Anyhow, sorry for the novel. I hope this information helps someone. Peace and good health to all!
From a chemical stand point, gas solubility in water is proportionate to pressure and temperature; introducing water at the bottom of a 30-ft standpipe for example will double the pressure, but since the bubbles will quickly rise to the surface, the full extent of the increased solubility will not be realized unless the higher pressure is maintained at a constant rate. The rate as opposed to the extent of the transfer of said gas into liquid is proportionate to the contact time and interfacial surface area. Surface agitation is not the end all determining factor here. The latter is inversely proportational to the cube of the bubble radius, so delivery of the gas in a form of tiny bubbles is far more rapid than for an equivalent volume of larger bubbles or solid stream.
To break that down for some of you that may be on your second bowl by now, airstone versus open line reaches the same goal eventually, but the airstone is the fastest most efficient method due to the spread of bubbles. I'm sure this has been covered in this forum, but I want to make it definitively clear.
At the ideal temperature of 20-22 celcius (68-71.6 fahrenheit) the water can only hold about 9 ppm dissolved oxygen. We can temporarily raise the dissolved oxygen levels by chemical reaction, such as adding H2O2 or more permanently raise it by causing waves at the surface with air pressure... Biochemical oxygen demand for the cannabis plant is only about 7 ppm to flourish in a constant water suspension. Watching frothing bubbles in a bucket is sure neat, and might sound relaxing for the first hour or so, but all you really need is enough air to have a light champagne sparkle that hits the lid of your container just barely. When you lift your lid after a day, and water drips at all, you're good. Before the nay-sayers in the crowd dismiss me as a lunatic, start shouting that I am a heretic and their crazy powerful pumps and powerheads own all; I'll tell you a little about what I did so you can reproduce it yourself.
My first grow involved four 18 gallon Rubbermaid containers and four Tetra Tec DW96-2 air pumps and 16 el-cheapo Wal-Mart airstones. I noticed something when one of my pumps failed (one of the diaphragms tore,) and I was forced to canabilize a cheap pump from my fish tank (sorry cichlids, my ladies need it more than you,) I had far less surface agitation/water movement, but my plants did absolutely fine all through the rest of their vegetative growth and flower stages. Curiousity got the best of me after this event... I went all mad scientist on the ladies with a gang valve to control the flow rate into the tub. Bare with me here, I am trying to explain it as simple as I can, but I sometimes have problems talking to the people outside of the walls of my head. hoo-hoo!
The Azide-Winkler method is widely known to the majority of chemists, and here's a break-down for you non-chemically inclined people... You start out with a 300 mL nalgene (or glass) bottle that has an air tight seal or stopper, ensuring that it has time to settle and no bubbles are visible. You generally don't want any bubbles when collecting your water sample, but sometimes it's unavoidable. I turned off my air pumps about 20 minutes before I collected my test samples. When the bubbles have settled, add 2 mL of manganese sulfate to your bottle by inserting a standard calibrated chemical dropper just below the water surface. Be careful though, if your re-agent is added above the surface you will introduce oxygen and your sample will become invalid. Squeeze the dropper slowly ensuring there are no bubbles being formed. Add 2 mL of alkali-iodide-azide re-agent in the same manner, remember, no bubbles! Close your bottle up gently, and mix it via inversion (turn it upside down, then turn it upside down again.) If you see any air bubbles, game over, start again. You'll start to see a cloud of brownish-orange junk. When it settles to the bottom, mix it via inversion again. Let it settle for a short period. I usually play tetris on my phone until I lose, then get back to it. Add 2 mL sulfuric acid via a chemical dropper from ABOVE the surface of the water. Close your bottle again, invert it over and over again to mix. At this point the sample can be stored for 7-12 hours in a cool dark place [this is dependent on your seal]. If you're anything like me, it's time to go crack a beer and eat a burger because you had to start over so many $%@* times. In a glass container, titrate 200 mL of the sample with sodium thiosulfate until it's a pale straw color. Titrate it slowly with your titrant solution one drop at a time into the container, stiring very gently just to make a swirl after each drop. Add 2 mL of starch solution, a blue color should be coalescing. Slowly titrate the solution until your sample turns clear. Only one drop too many of titrant will destroy your blue color, so be careful that each drop is fully mixed into your solution before adding the next. I generally do this in front of a white wall, or over a piece of high intensity white inkjet paper just to be absolutely sure of the colors in the container (I do the same thing with those annoying color pH test kits). The total concentration of dissolved oxygen is equivalent to the number of mL of titrant used. Each mL of sodium thiosulfate added equals about 1 ppm dissolved oxygen.
Utilizing the above methodology for measurement, I've established that nearly every strain of cannabis I have grown in the past 6 years only requires 7 ppm total dissolved oxygen. I gave up on looking for differences in 7 vs 14 ppm dissolved oxygen in DWC containers after seeing six different strains of four plant test samples per strain perform essentially the same. One thing that more dissolved oxygen does help with though, is keeping silly organisms like pythium in check. I'm sure you're already saying "duh!" or something like that in your head, but for the record I always introduce H2O2 every water change so I rarely worry about it in the long run. Die little eukaryotes, die! It also manages to keep my roots nice and white like my teeth. I urge people to re-create my experiment and test some rooted clones to see if you have any strains/phenotype that require or respond to more oxygen. The following strains were tested for 7 ppm survivability with no slow down in observable growth rate (subjective I know, but I went by height, internode spacing, stem thickness, and total plant diameter):
Skunk [red hair], reminded me of the 80s indoor strain that were so common, bag seed from a friend
Nirvana White Rhino
Nirvana AK-48
Nirvana Pure Power Plant
Reservoir Sour Diesel
Sensi Silver Haze
If we can form some type of database of oxygen level requirements for our plants, growing efficiency and sanity (because air pumps are loud) will increase. None of my plants showed any sign of slow down until levels reached 6 ppm, at which point growth rates during vegetative stage were days behind the other clones, but still surviving. At 4 ppm, plants began to droop as if they were overwatered and drowning. It wasn't until 2 ppm that I could reliably commit the horrible act of killing my ladies.
I think this is attributed to the roots getting added oxygen from hanging freely in the space between the water and the net pots, increasing their survivability chances. Too bad that they were basically eating themselves, but didn't live long enough to show me what they were eating. More oxygen than 14 ppm, did something for those that are wondering. It increased evaporation rate! (duh, a more gaseous state = higher evaporation) I couldn't raise the levels high enough to actually do harm to the plants, but I did notice at 14 ppm constant that my nutrient ppm seemed to not drop as fast. Possibly the plants not being able to eat fast enough due to a defensive mechanism? Maybe the evaporation rate causing the nutrient solution to be more volume versus water available? Got me, the girls wouldn't tell me if they were not getting what they needed or not, they stayed green. Any plant physiologists in the crowd want to chime in? I keep telling my plants that communication is the key to every healthy relationship, but I always get the cold shoulder. Anyhow, sorry for the novel. I hope this information helps someone. Peace and good health to all!
) I'd guess the strengthening process of the roots via motion would probably provide benefits, but on the other hand it also seems like the plant would have to devote extra energy to grow thicker roots, rather than more roots. 
